4 POPULAR GEOLOGY. 



If SO, then Sliibden dale must have been at that time the bed of some deep 

 sea. What a thought was that ! To think that I was wandering on an 

 old sea bottom, among the remains of animals that existed myriads of ages 

 before man was created! And when I saw in our stone-quarries at 

 Northowram, and the ironstone beds of Low Moor, large specimens of 

 fossil trees, such as the beautiful Lepidodendron, and the ornate Uloden- 

 dron, and the tall reed plants (Calamites) with fluted stems, of the same 

 family as our canes and the horse-tail plants, or the fluted and carved 

 stems of the Sigillaria, which grew in such profusion as to form the chief 

 part of our coal-beds; and all of them belonging to genera which have 

 long since passed away, I wondered how they came there, and what sort of 

 climate they grew in, and hqw they passed away when their appointed 

 time had come. And thus led on, like many others, I could not leave ofE 

 until I had learned the story from the rocks themselves. 



Geology treats of the structure, mode of formation, and order of the 

 rocks that form the crust of the earth, and also describes the fossil remains 

 of plants and animals which they contain. All the various kinds of rocks 

 which form the earth's crust may be divided into two great classes. 

 Stratified and Unstratified. 



1. Unstratified or igneous rocks are those whicli owe their origin to 

 subterranean heat, as granite, basalt, &c. These form the fomidatiou 

 upon which aU the other rocks are laid. 



2. Stratified or aqueous rocks have been formed out of the waste of 

 the igneous rocks, through the agency of moving water, and have been 

 deposited and arranged in layers at the bottom of rivers, estuaries, lakes, 

 and seas. 



The smrface of the earth is continually being wasted by a 

 multitude of causes, such as rain, wind, fro.st, snow, ice, and the never- 

 ceasing action of the breakers on the sea-coast. Every rill and stream 

 carries more or less of this dehris or waste of material into the rivers and 

 seas, where it is spread out in layers and hardened or compres^d into 

 rocks. This levelling process would go on until every particle of land had 

 been swallowed up by the sea, if it Avere not for another great force which 

 acts as a great counterpoise to the great leveller, Avater, and that is heat. 

 Volcanoes and earthquakes are tAvo great agents, sometimes forming peaks 

 10,000 feet high, and at other tunes raising islands out of the ocean in a 



